I bought a well used police trade-in 5906. I replaced the grip and all springs. Right now I am running a 14lb recoil and 20lb hammer spring. The problem is the inside of the pistol gets dirty inside real quick. I checked the fired cases and there are no blown primers. It looks to me that the pistol is unlocking too soon and allowing some gas to blow back into the action. Any ideas?
5906 unlocking too soon?
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Doc1500
Member
I'm definitely not an expert but a quick guess would be too light of a recoil spring. I don't know the lb of the factory one
I put in a 17lb recoil spring and shot 20 rounds of Speer 124gr TMJ and still have quite a bit of soot in the action. My 4006 does not do this and that is why I am asking. I ordered extra power hammer springs from Wolff and will see if that helps. Thanks for your help DOC1500.
You might also check the specs on the chamber in terms of correct size and depth (no-go gauge), and the barrel dimensions and condition (evidence of damage).....particularly the condition and spec ( length and width) of the tab at the rear of the barrel hood and the bottom of the foot that cams up on top of the pin on the slide stop. Do the slide and the frame match up at the rear of the slide when the gun (slide) is closed? (is the slide overrunning the frame when the gun is assembled and the slide is closed?)
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fiasconva
Member
My first question would be what brand of ammo are you using? If it's Remington UMC that could be the problem. It is some nasty stuff. Some of the others, especially the bulk ammo aren't much cleaner.
Doc1500
Member
I don't believe a heavier hammer spring is going to change any of that except for make your trigger pull heavier. I would try an 18 - 17 pound recoil spring.
Fishinfool
Member
I am not all that familiar with the older S&W auto pistols, but a couple questions come to mind.
Are there "swipe marks" caused by the firing pin on the primers of fired cases? That is often a sign of early unlocking. Are the once fired cases sooty - dirty as well? That indicates a round without enough oomph to seal the case against the chamber when firing. Doubtful, but not unheard of in factory ammo. Might be wrong, but I think the gun would have to be grossly "out of time" to be dumping powder residue into the action, enough so that you would be experiencing other signs, like swelled / blown case webs.
Had one of the new "wonder pistols" from Taurus about 15 years ago in 9mm. Factory defective machining caused it to unlock way to early in the cycle. Blown case heads and a cracked frame were the result of the first box of factory ammo thru it.
Larry
Are there "swipe marks" caused by the firing pin on the primers of fired cases? That is often a sign of early unlocking. Are the once fired cases sooty - dirty as well? That indicates a round without enough oomph to seal the case against the chamber when firing. Doubtful, but not unheard of in factory ammo. Might be wrong, but I think the gun would have to be grossly "out of time" to be dumping powder residue into the action, enough so that you would be experiencing other signs, like swelled / blown case webs.
Had one of the new "wonder pistols" from Taurus about 15 years ago in 9mm. Factory defective machining caused it to unlock way to early in the cycle. Blown case heads and a cracked frame were the result of the first box of factory ammo thru it.
Larry
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I have been using Speer Gold Dots and TMJ ammunition. But I think Armorer951 hit it. This barrel is done. The flat on the bottom of the barrel is penned from hitting the slide stop. There is a hump at the front of the flat. Thanks folks for showing me what to check. It's a shame there are no barrels for these pistols that are better than what I have.
You should be able to find a suitable barrel on Ebay, there are normally lots of good examples avalable. If not, Numrich has new and used barrels in stock. I would also replace the slide stop if it looks bad. Fitting should not be required. If you decide to buy a new barrel, the tab on the barrel hood may need to be fit for clearance.
See Numrich link for bbl info:
Smith & Wesson Model 5906 Parts | Gun Parts Corp.
Here's my old police 5906 trade in....new rear sight, new grips, new springs, install decock only safety lever, a good glass beading.......it's good as new. The Sherman tank of "all-stainless" autos.
See Numrich link for bbl info:
Smith & Wesson Model 5906 Parts | Gun Parts Corp.
Here's my old police 5906 trade in....new rear sight, new grips, new springs, install decock only safety lever, a good glass beading.......it's good as new. The Sherman tank of "all-stainless" autos.
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This one has the 0.395" barrel hood. I thank you folks for helping me out and I think I will just shoot it the way it is. I can't find a new barrel and it's not splitting or tearing off case heads, just not what I wanted it to be. Thanks again for your help.
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LVSteve
Member
The peening suggests a former owner ran a lot of hot rounds with a weak recoil spring.
mrmike7189
Member
Nice looking Sherman Tank
It may be a sherman tank, but the old Ruger semi autos were even stronger built. I like them both. Too bad that everything built today is polymer!
You should be able to find a suitable barrel on Ebay, there are normally lots of good examples avalable. If not, Numrich has new and used barrels in stock. I would also replace the slide stop if it looks bad. Fitting should not be required. If you decide to buy a new barrel, the tab on the barrel hood may need to be fit for clearance.
See Numrich link for bbl info:
Smith & Wesson Model 5906 Parts | Gun Parts Corp.
Here's my old police 5906 trade in....new rear sight, new grips, new springs, install decock only safety lever, a good glass beading.......it's good as new. The Sherman tank of "all-stainless" autos.
It may be a sherman tank, but the old Ruger semi autos were even stronger built. I like them both. Too bad that everything built today is polymer!
jbtrucker
Member
Too bad about your pistol maybe find another in better shape. Couple years ago bought a barrel from Midway for my 5906 , It was junk and no way to be machined to fit. Returned it for a refund really didn't need an extra barrel anyway. This one is my second pistol bought few years ago after a 469 I stupidly sold .
Attachments
That peening you describe could be from a lot of mileage or... from running an extra power recoil spring which slams the pistol into battery with much more force than it was designed to tolerate. Some wear and some small degree of plastic deformation of the steel in that area is quite normal in a well used pistol. Weak worn out springs and hot loads will batter other areas, not this.
Regarding early unlocking...
Some ammo is just dirty, I have some GI surplus 45 Match Wadcutters TZZ headstamp made in '89 that's just filthy. I shoot one mag of that stuff and my 4506 is caked with junk inside. So, I would not immediately assume dirty = early unlocking without other evidence. Check fired case for bulging above the extractor groove. Check for firing pin drag marks on the primers indicating early unlocking...
Credit where credit is due...I scrounged that pic from a web search.
Check extractor grooves on fired brass for unusual or deep gouges from the extractor, this and bulged brass indicate extracting while the brass is still pressurized.
Extra power recoil springs have about zero effect on the timing of unlocking from battery and will likely cause more problems so don't do that. If you want to experiment with spring weights to retard the timing of unlocking, put a heavier than stock mainspring in the gun. That spring driving your hammer is the one controlling timing of unlocking when the slide is at rest in battery.
Also, bear in mind what you have there is a mass produced service pistol, it's a fighting gun not a tight match gun. While I expect the chamber in a service pistol to be properly headspaced, I also expect it to be somewhat loose in diameter to aid reliable extraction and be able to continue working when it's really dirty.
Could be your chamber was cut a little loose and just as easily could be a previous owner did a little throating. Anyway there's no way to be sure without examining the thing.
If you have a dial or digital caliper... Measuring the ID of the chamber at .200 forward of the breechface it should be .3913". All the way in at the point the cartridge headspaces the ID is .3810. Yes the 9mm chamber has a significant taper and there is a diameter tolerance of up to +.004". This is all from the SAAMI chamber drawings.
How's the rifling look?
Cheers
Bill
BMCM, the chamber is pretty large from what I came up with. .396" and .387" for the chamber and the barrel lands are pretty shallow to me but I'm not sure what a new barrel for a 5906 looks like inside. Yes I'm aware of the recoil spring not doing much for slide speed going back but sure makes a difference going forward into lock-up. I don't know why they are called recoil springs, should be called return spring or slide rebound spring or something like that. I think that's why the hammer spring is called a "main" spring. I have some new hammer springs on the way and will see if it helps a little. Also, I can't figure how the metal being pushed back on the barrel flat (lack of better words) could cause early unlocking. Does it work like a barrel link in a 1911 or something?
Armorer951, I measured between barrel hood and breechface on slide and got .005" with barrel pushed forward. I don't have any go/no-go gages for 9X19 but using a new cartridge I got .015" from back of cartridge to end of barrel hood.
Correct SAAMI chamber depth should be .754" (.010"). All of the chambers in the barrels I have range from .760" to .764". (Measuring from the end of the tab down to the end of the chamber cutout) The .764" barrel is new and has never been fit to a slide. The gauge in the hood provides enough space to accomodate some variance in OAL casing measurements, and small differences in rim thicknesses, and to accomodate clearance for proper unlocking of the barrel from the slide.
The manual lists the "maximum" hood gauge, between the hood extension and rear of the the frame cutout (when fitting new barrels) as .005". Based on your info, and if you don't see any damage (peening) to the barrel lug recess in the slide, or damage on the barrel lug in front of the hood, or to the front of the hood itself, I would say, gauge wise, the barrel appears to be OK, other than the chamber being a bit deep. This diagnosis would also depend on the extent of the damage you are seeing on the barrel foot. I'm not sure if the depth of your chamber could account for some of the soot and debris you are seeing inside the frame or not, perhaps so.
The manual lists the "maximum" hood gauge, between the hood extension and rear of the the frame cutout (when fitting new barrels) as .005". Based on your info, and if you don't see any damage (peening) to the barrel lug recess in the slide, or damage on the barrel lug in front of the hood, or to the front of the hood itself, I would say, gauge wise, the barrel appears to be OK, other than the chamber being a bit deep. This diagnosis would also depend on the extent of the damage you are seeing on the barrel foot. I'm not sure if the depth of your chamber could account for some of the soot and debris you are seeing inside the frame or not, perhaps so.
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